1. Field of the Invention
The present invention is generally in the field of tissue engineering, and more specifically is a means for obtaining stem cells for seeding onto scaffolding for regeneration or repair of tissue, bone and other organs.
2. Description of the Background Art
The scarcity of human donor organs for transplantation is a growing problem. Despite aggressive public awareness campaigns the numbers of qualified organ donors has changed little in the last 20 years while the demand has grown at a rapid pace. In addition, allogeneic organ transplantation is still associated with a high frequency of complications due to immune rejection. Attempts to address this crisis have included development of ex vivo and implantable synthetic organ support devices such as pump devices for cardiac support and use of organs from other species (xenotransplantation). Xenotransplantation has been refined to include development of chimeric donor animals yet is still unperfected and subject to possible consequences such as the transmission of zoonoses.
Human stem cells are totipotential or pluripotential precursor cells capable of generating a variety of mature human cell lineages. This ability serves as the basis for the cellular differentiation and specialization necessary for organ and tissue development. Recent success at transplanting such stem cells have provided new clinical tools to reconstitute and/or supplement the bone marrow after myeloablation due to disease, exposure to toxic chemical or radiation. Further evidence exists which demonstrates that stem cells can be employed to repopulate many, if not all, tissues and restore physiologic and anatomic functionality. Evidence to date indicates that multipotent or pluripotent stem cells are directed to differentiate into specific mature cell lineages based on the physical and biochemical environment that they are delivered. There is also evidence that these cells can migrate from normal to abnormal or defective tissues and repopulate those areas in a very focused and specific manner.
The application of stem cells in tissue engineering, gene therapy and cell therapeutics is also advancing rapidly.
Many different types of mammalian stem cells have been characterized. For example, embryonic stem cells, embryonic germ cells, adult stem cells or other committed stem cells or progenitor cells are known. Certain stem cells have not only been isolated and characterized but have also been cultured under conditions to allow differentiation to a limited extent.
Despite considerable advances made in controlling differentiation of stem cells into mature cells and tissues, actual development of the complex architecture of solid organs has not been accomplished. Tissue engineering has therefore directed attention at growing component tissues and then assembling those components into useful structures.
It is therefore an object of the present invention to provide methods to remove the cellular content of tissues while preserving the extracellular matrix architecture coupled with advanced understanding of stem cells, which can be seeded with cells to yield whole organs with the anatomic and physiologic features of native organs.